1. Field of Invention
This invention relates to a method for fabricating an image sensor, wherein the image sensor is applied in an electronic image recording apparatus.
2. Description of Related Art
Electronic image recording apparatuses, such as charge-coupled device (CCD) image recording apparatuses and complementary metal oxide semiconductor (CMOS) image recording apparatuses, have been widely used for image recording. As shown in FIG. 1A, the core of such an image recording apparatus typically includes an image sensor chip 10 and lenses 12 disposed thereover. The sensor chip 10 is formed with photosensitizing devices (not shown) like CCDs or photodiodes. The lenses 12 are fit in a lens barrel 14. The incident light 16 irradiates the chip 10 through the lenses 12.
The chip 10 is schematically illustrated in FIG. 1B in a magnified view, having a photosensitizing plane 110 defined by the photosensitizing devices and an interconnect dielectric layer 120. To improve the sensitivity of the photosensitizing devices, a planarization layer 130 and microlenses 140 with focusing capability are usually formed over the interconnect dielectric layer 120.
However, as shown in FIGS. 1A-1B, since the incident angle of the central incident light 16a is zero, the incident angle of non-central incident light 16b increases toward the edge of the chip 10 and the curvatures and the focal lengths of the respective microlenses 140 are the same, the distance between the focus position of the incident light 16b and the photosensitizing plane 110 increases toward the edge of the chip 10. Thus, the sensitivity of the photosensitizing device decreases toward the chip edge, which is a cause of the distortion in image recording.